1. Field of the Invention
The present invention relates to a mobile telephone system, and particularly to a cordless telephone system.
2. Description of the Related Art
A cordless telephone system that indicates position information of a caller to a called side and position information of the called side to the caller is described in Japanese Patent Laid-open No. 328432/1993. This cordless telephone system will be described with reference to FIG. 1 and FIG. 2. FIG. 1 is a block diagram of the above-described cordless telephone system, which is made up of a main unit 51, a plurality of cordless telephone connectors BS1-BSn connected to main unit 51, and a plurality of cordless telephones T1-Tm. Each of cordless telephone connectors BS1-BSn forms a radio zone RZ1-RZn, respectively. Main unit 51 comprises call processing section 52, memory section 53, external line interface 54, channel switch 55, and cordless telephone connector interface 56.
Memory section 53 is written to and read out by call processing section 52 and includes position registration information memory section 531.
As shown in FIG. 2, zone information indicating the radio zones RZ1, RZ2, . . . RZn those are position-registered for cordless telephones, T1, T2, . . . Tm corresponding to the extension numbers "1000," "1001," . . . "2000".
Call processing section 52 manages position registration information memory section 531, controls connections between telephone lines L1-Lk and cordless telephones T1-Tm, and controls connections between cordless telephones T1-Tm. Of the various controls performed by call processing section 52, extension processing section 521 performs control relating to extension communications between cordless telephones T1-Tm.
External line interface 54 interfaces with telephone lines L1-Lk.
Channel switch 55 connects channels under the control of call processing section 52.
Cordless telephone connector interface 56 interfaces with cordless telephone connectors BS1-BSn.
Each cordless telephone Ti (1&lt;i&lt;m) has the following functions in addition to ordinary voice communication functions:
1. Numerals and letters indicated by display information sent from extension processing section 521 of main unit 51 by way of cordless telephone connector interface 56 and cordless telephone connectors BS1-BSn are shown on a display (not shown). PA1 2. The reception levels of radiowaves for control use outputted at fixed time intervals from each of cordless telephone connectors BS1-BSn are compared and the cordless telephone connector BSj (1.ltoreq.j.ltoreq.n) having the best reception state is detected. PA1 3. If the name of the cordless telephone connector stored in a transmission destination registration area (not shown) that is internally provided differs from the detected name of the cordless telephone connector BSj, the name of the cordless telephone connector registered in transmission destination registration area is rewritten to the detected name of cordless telephone connector BSj (the name of the cordless telephone connector stored in the transmission destination registration area indicates the transmission destination cordless telephone connector of the call establish message). PA1 4. If the name of the cordless telephone connector stored in the transmission destination registration area differs from the name of detected cordless telephone connector BSj, position registration information including the extension number assigned to cordless telephone Ti is transmitted to cordless telephone connector BSj.
At the main unit, moreover, position registration information including the extension number of cordless telephone Ti that is transmitted to cordless telephone connector BSj from cordless telephone Ti is sent to call processing section 52 through cordless telephone connector interface 56; and, based on the sent position registration information, call processing section 52 rewrites stored zone information corresponding to the extension number of cordless telephone Ti of the zone information stored in position registration information memory section 531 to zone information indicating the radio zone RZj formed by cordless telephone connector BSj. By means of this processing, cordless telephone Ti is position-registered in radio zone RZi.
Although the above-described cordless telephone system enables display of the position information of a communication partner terminal, but the position information indicates only the radio zone, particularly a particular vicinity within the zone cannot be indicated.
Furthermore, a plurality of cordless telephone connectors and systems for managing the plurality of cordless telephone connectors are required, resulting in a large-scale construction and system complexity. Moreover, telephones cannot be used beyond the range of the radiowaves of the cordless telephone connectors within this system.
Finally, such a system is vulnerable to invasion of privacy because location checking can be effected by any number of unspecified people.